what's this solving technique

Advanced methods and approaches for solving Sudoku puzzles

what's this solving technique

Postby docjohn » Fri Jan 07, 2011 7:25 pm

my first post to the forum,so please forgive me if I have sinned

I'm writing a sudoku solver and have run across this combination. 5's have a strong link in box 2 and box 7 so I'm assuming I can eliminate the 5's in box 5 (the x's)

I have written solving algorhythms for 2 string kites, turbot fish, skyscrapers, and x-wings but none of those methods can detect this pattern.

it resembles a turbot fish but not quite.

Does anyone out there know a name for this? Sashimi fish perhaps?

thanks in advance



'+-------------------------------+-------------------------------+-------------------------------+
'| - - - | - - 5 | - - - |
'| - - - | - - - | - - - |
'| - - - | 5 - - | - - - |
'+-------------------------------+-------------------------------+-------------------------------+
'| - - - | x - x | - - - |
'| - - - | x - x | - - - |
'| - - - | x - x | - - - |
'+-------------------------------+-------------------------------+-------------------------------+
'| - - - | 5 - - | - - - |
'| - - - | - - - | - - - |
'| - - - | - - 5 | - - - |
'+-------------------------------+-------------------------------+-------------------------------+
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Re: what's this solving technique

Postby lksudoku » Fri Jan 07, 2011 7:47 pm

You have a x-loop in your puzzle

Maybe there is a simpler technique describing this pattern, but if there isn't, you can consider this as x-loop

You can also remove 5 from more cells in boxes 2 and 8
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Re: what's this solving technique

Postby daj95376 » Fri Jan 07, 2011 8:01 pm

If you replace the empty cells in [b2] & [b5] with the (/) character, you'll see that the only place in [c5] for the candidate is r456c5 -- a Locked Candidate 2. (also called Claiming)

Code: Select all
+-------+-------+-------+
| - - - | / / 5 | - - - |
| - - - | / / / | - - - |
| - - - | 5 / / | - - - |
+-------+-------+-------+
| - - - | x - x | - - - |
| - - - | x - x | - - - |
| - - - | x - x | - - - |
+-------+-------+-------+
| - - - | 5 / / | - - - |
| - - - | / / / | - - - |
| - - - | / / 5 | - - - |
+-------+-------+-------+
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Re: what's this solving technique

Postby docjohn » Sun Jan 09, 2011 7:12 pm

X-loop! Cool! Thanks for the reply.

The eliminations if box 2 and box 8 (not box 7, typo, my bad) shouldn't apply. My intent was to was to have just two 5's in box 2 and box 8.

Thanks again. Love this forum
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Re: what's this solving technique

Postby JasonLion » Sun Jan 09, 2011 7:45 pm

docjohn wrote:5's have a strong link in box 2 and box 7
is the same thing as the / in daj95376's. A strong link means one or the other must be true, which means no other cell in that box can contain a 5, which is exactly what the / marks mean.
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Re: what's this solving technique

Postby docjohn » Tue Jan 11, 2011 4:53 am

got it! didn't know about the / but I do now

thanks for helping out a noob
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